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Most of my ‘big’ prints on the C-Bot have involved vases:  Large flat bases, thin walls, print fast.  I wanted to try something more ‘structural’:  Dense & flat & strong, but still take up most of the build volume.

So I printed a giant P: (you know, for ‘P’avey)

• 500 micron layer height, 1 shell, 2 floor, 2 roof, 20% infill.
• 1mm E3dD-v6 Volcano nozzle printing @ 30mm/sec.
• Fans on at layer 3, 25%.
• 210 deg blue GizmoDorks PLA on glass plate covered in wood glue slurry.
• Modeled in Maya, sliced in Simplify 3D.
• Just over 4 hours to print.

Came out really well actually, only thing that could be better is the top surface quality:  I either need one more roof layer (currently 2), or I’d need to up the infill to a higher percentage so the bridging wasn’t so far.  And it stuck really well to the wood-glue slurry on the glass build plate.

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Back on part 23 I added dual 12v 40x10mm cooling fans to the C-Bot: I’m guessing each was around 4cmf, for a total of 8cfm.  About the same cfm as the single 24v 40mm fan on my Replicator 1.  Thing is, the 1mm E3D-v6 Volcano nozzle I’m using is 2.5x as wide, and printing layers 2.5x as thick as the .4mm Mk8 nozzle on my rep1:  So, a huge increase in volume being extruded, but same cooling.  The results was, negligible:  Turning the fans on\off seemed to have no effect on the prints.

So, after much research online, I found a 12v ‘High Speed Delta Cooling Fan‘ on ebay, 40x30mm rated at 24cfm : I bought a pair of those, modeled a modified fan bracket based on what Carl Feniak had made (download the stl’s from Thingiverse), and hooked them up:

Pros:

• Huge amount of cooling, 48cmf combined.  If you point them towards the ground they act like hovercrafts.
• Don’t need any ducting, so much power.

Cons:

• Noise:  They sound like little turbines at full power.  Causes the stinkeye from the Mrs.
• On a torture test, the pressure actually blew a tower off the build platform (it was only anchored by a few mm of footing though).

Other:

• This could be a pro or a con based on how you look at it:  They cool so well, that the nozzle’s heater block couldn’t keep up:  Set at 210 degrees, it would steadily lower under 200 until I shut it down.  I had to use a spare strip of ceramic insulation tape (for a Replicator 2, fits great on the volcano though) to cover the heater block, then surround that with probably four layers of aluminum foil.  Now I can run the fans at 90% and not loose temp.

The Result:

• They definitely cool the pla down quickly, compared to no cooling at all.  Currently my biggest hinderance is that I’m low on filament, and the spools I have left have absorbed moisture, causing popping sounds during print, so I can’t get an accurate read on final quality.
• I can report though that bridging is much better:  I used to have to print three top layers to get a good finish, but I can drop that to two now.

Other things I’ve learned in the process:

• Hairspray : No good as a binder between the PLA and glass build platform:  The volcano prints pop right off within a few layers.  A 50/50 mix of wood glue & water though, like I have been using, works great.  On my rep1 I can use hairspray ok though, I figured it would work here too.
• Temp:  At 30mm/sec, I’ve been printing gray PLA at 210 deg successfully.  Tried lowering the temp to 200, but no dice:  The Bowden notched the filament.

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